Related papers: The CP Puzzle in the Strong Interactions
A non-axion solution to the Strong CP Problem is proposed that works even in the context of gravity-mediated supersymmetry breaking. Both $\epsilon'/\epsilon$ and indirect CP violation in the $B-\bar{B}$ are predicted to be unobservably…
A recent paper "What can solve the strong CP problem?" goes counter to conventional wisdom by arguing that the universe was in an initial state that combines different eigenstates of $\theta$ (of the theta vacuum of QCD), and asserts that…
We review recent work on the strong CP problem in the context of realistic string-inspired models. We discuss the various solutions, review the conjecture that CP is generally a gauged discrete symmetry in string theory and then consider…
We present a supersymmetric solution to the strong CP problem based on spontaneous CP violation which simultaneously addresses the affects coming from supersymmetry breaking. The generated CP violating phase is communicated to the quark…
I discuss how the solution of the $U(1)_A$ problem of QCD through the existence of the $\theta$-vacuum gave rise to the strong CP problem. After examining various suggested solutions to this problem, I conclude that the only viable solution…
We propose a non-universal $\mathrm{U}(1)_{X}$ gauge extension to the Standard Model (SM) and an additional Peccei-Quinn (PQ) global symmetry to study the mass hierarchy and strong CP problem. The scheme allows us to distinguish among…
Solutions of the Strong CP Problem based on the spontaneous breaking of CP must feature a non-generic structure and simultaneously explain a coincidence between a priori unrelated CP-even and CP-odd mass scales. We show that these…
The $U(1)$ global symmetry to solve the strong $CP$ problem could be the remnant of multi-$U(1)$ symmetries from QCD and hidden strong dynamics. Both Peccei-Quinn $U(1)$ and dynamical $U(1)$ are described uniformly, based on which we…
A very simple model is presented where all CP violation in Nature is spontaneous in origin. The CKM phase is generated unsuppressed and the strong CP problem is solved with only moderately small couplings between the SM and the CP violation…
Addressed is the question of whether a natural mechanism exists to resolve the strong CP problem. The analogous issue for the two-dimensional $CP^{N-1}$ models is analyzed using computer simulations.
We exhibit a solution to the strong CP problem in which ultraviolet physics renders the QCD theta angle physically unobservable. Our models involve new strong interactions beyond QCD and particles charged under both the new interactions and…
We reconsider the massless up quark solution of the strong CP problem. We show that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry. Reviewing the…
We show that the de Sitter quantum breaking bound when applied to QCD exposes the necessity of the axion solution to the strong CP problem. The Peccei-Quinn mechanism emerges as a consistency requirement independent of the naturalness…
One may argue that QCD solves the strong CP problem by itself, without having to introduce new symmetries and particles. To test this idea, a lattice simulation is performed. The problem is investigated in the CP$^3$ model first. It is…
These TASI lectures where given in 2018 and provide an introduction to the Strong CP problem and the axion. I start by introducing the Strong CP problem from both a classical and a quantum mechanical perspective, calculating the neutron eDM…
An approach to solving the Strong CP Problem in supersymmetric theories is discussed which uses abelian family symmetries to align the mass matrices of the quarks and squarks. In this way both the Strong CP Problem and the characteristic…
The proximity of the Peccei-Quinn scale to the scale of supersymmetry breaking in models of pure gravity mediation hints at a common dynamical origin of these two scales. To demonstrate how to make such a connection manifest, we embed the…
A broad experimental program is targeting the QCD axion band predicted by single-axion solutions to the strong CP problem. Multi-axion theories provide a well-motivated departure from this canonical picture, since additional states…
In this chapter we introduce the $\theta$-dependence and the topological properties of QCD, features of the strongly interacting sector which give rise to the strong CP problem in the more general context of the Standard Model of particle…
It is shown that the quark mass aligns QCD $\theta$ vacuum in such a way that the strong CP is conserved, resolving the strong CP problem.